As disclosed in March, Advanced Organic Chemistry, Second Edition, McGraw-Hill, New York, 1977, pp. 501-502; Olah, Friedel-Crafts and Related Reactions, Volume 2, Interscience Publishers, New York, 1963-1964, pp. 659-784; U.S. Pat. No. 2,516,971 (Galitzenstein et al.); Canadian Patent 1,135,268 (Harris); and the references cited therein, it is known that aromatic compounds can be haloalkylated by reacting them with a hydrogen halide and an appropriate aldehyde, or with an .alpha.-haloalkyl ether or an .alpha.-haloalkyl alkyl ether, in the presence of a Lewis acid or a proton acid as a catalyst, most commonly in the presence of zinc chloride.
The haloalkylations utilizing formaldehyde or a formaldehyde-derived ether have been successfully employed in providing fairly high yields of 1-halo-1-arylalkanes, and reasonably high yields of 1-halo-1-arylalkanes have sometimes also been obtained from haloalkylations utilizing higher aldehydes or ethers derived from them. However, it has frequently not been found possible to provide commercially acceptable yields of 1-halo-1-arylalkane from the higher aldehydes and ethers, especially when the aromatic compound has been one of the less reactive ones, such as a monoalkylaromatic hydrocarbon. There has been too much co-formation of diarylalkane by-product.
It would be desirable to find a way of increasing the 1-halo-1-arylalkane yields obtainable from such processes to provide a more economical method of preparing, e.g., the 1-halo-1-(4-alkylphenyl)alkanes used in known processes, such as those of U.S. Pat. No. 4,536,595 (Gardano et al.), Canadian Patent 1,197,254 (Francalanci et al.), British Patent 1,560,082 (Dynamit Nobel), Czechoslovakian Certificate of Authorship 219,752 (Palecek et al.), and Japanese Kokai 47-39050 (Miyatake et al.) and 52-111536 (Tokutake).
Copending application Ser. No. 295,017 (Knesel), filed Aug. 17, 1989, discloses methods of improving the ratio of 1-halo-1-arylalkane to diarylalkane; but Knesel's ratios are not acceptably high at a sufficient degree of conversion to provide the yields of 1-halo-1-arylalkane that are desired.